Embodiments of the present invention relate to cleaning a component used in the processing of a substrate in a process chamber.
To manufacture electronic circuits and displays, a substrate such as a semiconductor wafer or display, is placed in a chamber and processed in a plasma of process gas. For example, in a PVD process, a plasma sputters a target of sputtering material to deposit sputtered target material on the substrate. In a CVD process, a plasma of a deposition gas is used to deposit material on the substrate. In etch processes, a plasma is used to etch material on the substrate. The chamber has a number of components that are exposed to the plasma during processing, for example, a substrate support that holds the substrate, liners, gas distribution or exhaust rings, and focus rings.
In such substrate processes, the plasma forms process deposits on the surfaces of the chamber components that have to be periodically cleaned off. In one cleaning method, the chamber components are removed from the chamber and immersed in a cleaning solution, such as an acidic or basic solution. In another method, the component remains in the chamber, a cleaning gas in introduced in the chamber and a plasma is formed of the cleaning gas to clean off the process deposits. However, such cleaning methods often leave behind process deposits which are chemically adhered to the component or which are deposited in especially thick layers.
Components such as a gas distributors, liners and electrostatic chucks, are especially difficult to clean because they have holes in them for the passage of gas or for other reasons. For example, the gas distributor has a number of gas holes to release a processing gas into the chamber. An electrostatic chuck also has gas holes to release a heat transfer gas below the substrate. In a typically chuck, the gas holes are spaced apart and distributed around the ceramic surface to supply heat transfer gas to desired locations below the substrate. The holes are usually small to prevent plasma or glow discharges from forming inside the holes during use of the electrostatic chuck. Conventional cleaning processes often do not adequately clean off the process deposits formed inside the small holes by such a gas plasma. For example, acidic or basic solutions used in wet cleaning processes may not enter into the gas holes because they are either filled-up with process deposits or because surface tension forces prevent the solution from entering the small holes. In dry cleaning processes, the plasma also often does not permeate fully into the holes. When these holes are not properly cleaned, the electrostatic chuck provides an uneven distribution of gas behind the substrate, and the substrate is not properly cooled or heated. The same problem is faced when cleaning a gas distributor or liner having small gas holes.
Another problem arises when trying to cleaning process deposits on ceramic surfaces, such as a ceramic surface of a chuck. Ceramic chucks provide good tolerance to heat and resistance to chemical erosion from erosive gas plasma environments. However, PVD and CVD deposits often strongly adhere to the ceramic surfaces and are difficult to remove using conventional cleaning methods. The ceramic surface can be eroded by a chemically strong cleaning solution. The brittleness of the ceramic material also makes it difficult to clean the surface by abrasion, or to clean the gas holes in the ceramic material without causing fractures or micro-cracks in the ceramic. When a ceramic surface is damaged, the chamber plasma penetrates through the damaged areas to erode the exposed underlying surfaces, and can also cause arcing and electrical shorts with the chuck electrode, eventually leading to failure of the chuck during processing and loss of the substrate.
Thus, it is desirable to effectively clean a chamber component so that the component has desirable surface properties in a plasma processing environment. It is further desirable to uniformly clean all the gas holes in an electrostatic chuck or other component, so that the cleaned structure can provide a uniform distribution of gas in the chamber. It is also desirable for the cleaning process to provide consistent and reproducible cleaning results.